That is unusual. I wonder if JP accounts can no longer post to the EN forums as well. I used to post here from my JP account before it got converted to an NA one, and I posted help requests on the JP forum as well. I've seen some bilingual JP forum users come to post responses to us here as well. It makes no sense to have both languages of forum visible if we're not allowed to contribute to both, and there are plenty of bilingual people on both sides of the forum. That must have been a fairly recent change.
The reply button is gone, but the Reply with Quote is not, it just leads to an error saying that you don't have permission to access the page.